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Winch
A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the "tension" of a rope or wire rope (also called "cable" or "wire cable"). In its simplest form it consists of a spool and attached hand crank. In larger forms, winches stand at the heart of machines as diverse as tow trucks, steam shovels and elevators. The spool may also be called the winch drum. More elaborate designs have gear assemblies and can be powered by electric, hydraulic, pneumatic or internal combustion drives. Some may include a solenoid brake and/or a mechanical brake or ratchet and pawl device that prevents it from unwinding unless the pawl is retracted. History The earliest literary reference to a winch can be found in the account of Herodotus of Halicarnassus on the Greco-Persian Wars (Histories 7.36), where he describes how wooden winches were used to tighten the cables for a pontoon bridge across the Hellespont in 480 B.C. Winches may have been employed even earlier in Assyria. By the 4th century BC, winch and pulley hoists were regarded by Aristotle as common for architectural use (Mech. 18; 853b10-13).J. J. Coulton, “Lifting in Early Greek Architecture,” The Journal of Hellenic Studies, Vol. 94. (1974), pp. 1-19 (12) Applications Besides industrial applications (e.g. in cranes), winches are used for Breakdown trucks and towing cars, boats, or gliders. There are several winches on almost every boat or ship where they are used to pull anchor or mooring lines, halyards, and sheets. Common applications on vehicles are to load trailers on early tank transportes were fitted with Heavy Duty winch units for loading. A lot of the early Steam engine had a winch built in for a variety of purposes, and the later Showman's engines had a Gin pole that was used to build the rides up with. A large number of the Field Marshall tractors were sold with winches as they replaced steam engines an hydraulic cranes had yet to gain acceptance for every day jobs. They were offered with Light medium or HD versions by Marshall, Sons & Co. or from other manufacturers. Used with pulley (Snatch) blocks and suitable anchor points huge loads can be moved in a controlled maner with a winch. The use of Snatch blocks increasing line pull but reducing speed of the line. During WW II a number of trucks and tractors were fitted with winch drums for launching and recovering anti-aircraft balloons to protect towns and Airfields during the Blitz. The rope is usually stored on the winch, but a similar machine that does not store the rope is called a capstan. When trimming a line on a sailboat, the crew member turns the winch handle with one hand, while tailing (pulling on the loose tail end) with the other to maintain tension on the turns. Some winches have a "stripper" or cleat to maintain tension. These are known as "self-tailing" winches Mark Smith. The Annapolis Book of Seamanship. 1999 Simon & Schuster. Winches are frequently used as elements of backstage mechanics to move scenery in large theatrical productions. Winches are often embedded in the stage floor and used to move large set pieces on and off. Winches have recently been built specifically for water and snow sports (e.g. wakeboarding,wakeskating, snowboarding, etc.). This new generation of winches are designed to pull riders swiftly across a body of water or snow by simulating a riding experience that is normally supplied by a boat, wave runner, or snow mobile. Modern oilfield trucks use a HD winch and Shear legs fitted to the tractor unit to load skid mounted modules for transport, rather than bring in cranes which require a lot of setting up and good ground. Power line installation is a specialist job that uses tractors fitted with a winch and guide pulley frame to hoist up and tension power cables via temporary guide pulleys attached to pylons, prior to the insulated hangers being attached. Other Types Tirfors Tirfors also commonly known as griphoists are winches that instead of using spools to move rope or wire through the winch use self-gripping jaws. Powered by moving a handle back and forth they allow one person to move objects several tons in weight. Snubbing Winch This is a vertical spool with a ratchet mechanism similar to a conventional winch, but with no crank handle or other form of drive Maritime Industry Dictionary definition: http://www.m-i-link.com/dictionary/default.asp?term=snubbing+winch. The line is wrapped around the spool and can be tightened and reeled in by pulling the tail line, the winch takes the load once the pull is stopped with little operator tension needed to hold it. They also allow controlled release of the tension by the operator using the friction of the line around the ratcheted spool. They are used on small sailing boats and dingies to control sheets and other lines, and in larger applications to supplement and relieve tension on the primary winch mechanisms. The largest electric drive winch in the world is placed on the Balder, a construction ship. It is used as a mooring line deployment winch with a diameter of 10.5 meters and a safe working load of 275 metric tonnes. Manufacturers of Industrial winches * Auto-Mower Company in the UK * Broughton - UK * Gar Wood in the USA (often used in recovery vehicles) * Hyster * Marshall, Sons & Co. (fitted to the Field Marshall tractor) Machines with winches attached * Auto-Mower Line Errector * Caterpillar Crawlers fitted with Cable Control Units (CCU) * County tractors ** County Full Track * Fordson tractors * Roadless Fordson half-track * Scammell Explorer * Scammell Pioneer See also * Pulley * Steam donkey * Glossary Index * Crane * List of Types of Agricultural Machinery References External links * Article about boat winches Category:Mechanisms Category:Glossary Category:Winches